1. Field of the Invention
The present invention relates to a multistage high-pressure compressor having a multistage compression mechanism section which compresses an intake working fluid so as to generate a high pressure working fluid. More particularly, the present invention relates to a torque fluctuation suppressing device in an electric motor of the multistage high pressure compressor. The present invention also relates to a sealing device of a multistage high-pressure compressor, and more particularly to a seal structure between a cylinder and a member surrounding the outer periphery thereof.
2. Detailed Description of the Prior Art
A multistage high-pressure compressor including an electric motor provided in a lower part thereof and a compression mechanism section provided in an upper part thereof has been known. In such a multistage high-pressure compressor, the compression mechanism section has a plurality of compression sections, and reciprocates a piston with respect to a cylinder by the rotation of a rotating shaft which extends upwardly from the electric motor. The reciprocation of the piston causes an intake working fluid to be compressed through a plurality of compression stages, thereby generating a high-pressure working fluid. Examples of this type of multistage high-pressure compressor include a multistage compression device which is one of high-pressure gas compressors invented by the present applicant prior to the filing date of the present application. Such a multistage compression device is described in Japanese Patent Application Nos. 11-81781 and 11-46748, for example.
FIG. 1 illustrates a prior art showing a relationship between a compression mechanism section and an electric motor. In FIG. 1, reference numeral 20 denotes an electric motor. The electric motor 20 includes a stator 22 which has a coil 21 and is fixed to an inner surface of a motor casing 24, and a rotor 25 which is provided inside the stator 22 and spaced from the stator 22 by a predetermined air gap. A rotating shaft 23 of the rotor 25 extends upwardly. A compression mechanism section 26 is provided above the electric motor 20. Reference numerals 27 and 28 denote housing members attached to the upper and lower sides of the motor casing 24. The motor casing 24 and the housing members 27 and 28 together contain the electric motor 20. Reference numerals 29 and 30 denote bearings for rotatably supporting the rotating shaft 23. Reference numeral is a detent key for preventing the rotor 25 from rotating with respect to the rotating shaft 23.
In the above-described structure, a piston 32 is reciprocated with respect to a cylinder 31 of the compression mechanism section 26 by the rotation of the rotating shaft 23. The reciprocation of the piston 32 causes a working fluid such as an intake gas to be compressed through four stages, thereby generating a high-pressure gas. The structure and operation of a high-pressure compressor of such a four-stage compression mechanism are described in the aforementioned Japanese Patent Application Nos. 11-81781 and 11-46748.
As illustrated in FIG. 1, the electric motor 20 includes the rotor 25, in which a circular plate 33 for receiving the lower surface of the rotor 25 is fixed to the lower end of the rotating shaft 23 by a bolt 34 which is screwed into the rotating shaft 23, thereby supporting the rotor 25 with respect to the rotating shaft 23.
The detent key 35 which is disposed between the rotating shaft 23 and the rotor 25 is for preventing the rotor 25 from rotating with respect to the rotating shaft 23. The whole detent key 35 is included in the rotor 25.
As described above, the prior art requires the circular plate 33 which is provided for supporting the rotor 25 with respect to the rotating shaft 23 of the electric motor 20. Thus, a torque fluctuation of the electric motor 20 occurs in the prior art case, and neither structures nor effects for suppressing such a torque fluctuation are provided in the prior art.
The second problem to be solved by the present invention will now be described in connection with a prior art multistage high-pressure compressor shown in FIG. 2 to FIG. 5. A multistage high-pressure compressor 100 includes four compression sections (compression stage sections) 101, 102, 103, and 104, i.e., the compressor is the four-stage compressor. The compression sections 101 and 103 are disposed on a horizontal axis 106, and the compression sections 102 and 104 are disposed on a horizontal axis 105. A reciprocal compression mechanism is composed of cylinders 71, 72, 73, and 74 which are fixed members, and pistons 51, 52, 53, and 54 which are movable members reciprocating therein, arranged on the axes 106 and 105.
First, a working fluid taken in from an intake tube 118 is compressed at the first stage compression section 101. Next, the working fluid compressed at the first stage compression section 101 enters the second stage compression section 102 via a conduit 5 to be compressed. Then, the working fluid compressed at the second stage compression section 102 enters the third stage compression section 103 via a conduit 6 to be compressed. Thereafter, the working fluid compressed at the third stage compression section 103 enters the fourth stage compression section 104 via a conduit 7 to be compressed. The thus-obtained high-pressure working fluid with predetermined pressure and flow rate is output from a discharge tube 8.
The working fluid in such a multistage high-pressure compressor 100 is a gas such as nitrogen, a natural gas, sulfur hexafluoride (SF6), and an air. The multistage compressor 100 can be applied to a natural gas filling machine for filling a natural gas into a Bombe (cylinder) of an automobile using a natural gas, a high pressure nitrogen gas supply to a gas injection molding machine which uses a high pressure nitrogen gas during injection molding of synthetic resin, filling machine for filling a high pressure air into an air Bombe, or the like.
In the multistage high-pressure compressor 100, the piston 51 in the first stage compression section 101 and the piston 53 in the third stage compression section 103 are connected to a yoke 1A on the axis 106. A cross slider 2A which is movably provided so as to cross the axis 106 in the yoke 1A is connected to a crankshaft 4 via a crank pin 3. The axes 105 and 106 cross at an angle of 90 degrees as viewed from the above. The piston 52 in the second stage compression section 102 and the piston 54 in the fourth stage compression section 104 are connected to a yoke 1B on the axis 105. A cross slider 2B which is movably provided so as to cross the axis 105 in the yoke 1B is connected to the crankshaft 4 via the crank pin 3.
The crankshaft 4 is rotated by the electric motor 20 (see, e.g., FIG. 1) which is provided below the compression sections 101 to 104. The rotation of the crankshaft 4 causes the crank pin 3 which is provided eccentrically with respect to the crankshaft 4 to be rotated around the crankshaft 4. Regarding the yoke 1A, a displacement of the crank pin 3 in the direction of the axis 105 is accommodated by the movement of the cross slider 2A, and a displacement of the crank pin 3 in the direction of the axis 106 is accommodated by the movement of the yoke 1A. Accordingly, the pistons 51 and 53 reciprocate only in the direction of the axis 106.
On the other hand, regarding the yoke 1B, a displacement of the crank pin 3 in the direction of the axis 106 is accommodated by the movement of the cross slider 2B, and a displacement of the crank pin 3 in the direction of the axis 105 is accommodated by the movement of the yoke 1B. Accordingly, the pistons 52 and 54 reciprocate only in the direction of the axis 105.
FIG. 5 is a cross-sectional view showing the structure of the first stage compression section 101 of the multistage high-pressure compressor 100. The first stage compression section 101 includes a first compression chamber 58 and a second compression chamber 59 provided on opposite sides of the piston 51.
When the piston 51 advances, a working fluid is taken into the first compression chamber 58 in directions indicated by arrows via opened valves e and f, with valves a and b being closed. A working fluid in the second compression chamber 59 is simultaneously compressed. When the compressed working fluid in the second compression chamber 59 reaches a predetermined pressure, the working fluid is discharged to the outside via opened valves c and d. Thereafter, the working fluid is sent to the second stage compression section 102 via the conduit 5 as illustrated in an arrow shown in FIG. 3 and FIG. 5.
When the piston 51 retracts, the valves e and f are closed, and the working fluid in the first compression chamber 58 is compressed. When the compressed working fluid reaches a predetermined pressure, the valves a and b are opened, thus discharging the working fluid to the second compression chamber 59. Reference numeral 60 denotes a rod guide for guiding a connecting rod 57 so that the connecting rod 57 smoothly reciprocates between predetermined positions without vibrations.
As described above, the first stage compression section 101 of the multistage high-pressure compressor 100 employs a double compression mechanism (double action mechanism) such that a working fluid is taken in, compressed, and discharged through two steps in the single cylinder 71. Each of the second stage compression section 102, the third stage compression section 103, and the fourth stage compression section 104 employs, instead of the double compression mechanism as that of the first stage compression section 101, an ordinary arrangement, so-called a xe2x80x9csingle action mechanism,xe2x80x9d where the intake gas is compressed through a single stage compression in the cylinder by reciprocating the piston with respect to the cylinder.
In the above-described structure, the pressure of a gas which is the working fluid taken in from the intake tube 118 is generally about 0.05 MPa(G), and the gas is compressed to about 0.5 MPa(G) in the first stage compression section 101. The compressed gas is supplied to the second stage compression section 102 through the conduit 5. Then, the gas is compressed to about 2 MPa(G) in the second stage compression section 102. Thereafter, the compressed gas is supplied to the third stage compression section 103 through the conduit 6. The gas is compressed to about 7 to 10 MPa(G) in the third stage compression section 103. Thereafter, the compressed gas is supplied to the fourth stage compression section 104 through the conduit 7. The gas is compressed to about 20 to 30 MPa(G) in the fourth stage compression section 104. The thus-obtained high pressure gas (high pressure working fluid) is supplied from the discharge tube 8 to an accumulator. The high-pressure gas is supplied from the accumulator into an article of interest, e.g., a gas injection molding machine, an air Bombe, or the like.
In the above-described prior art, the respective cylinders 71, 72, 73, and 74 of the first stage compression section 101 through the fourth stage compression section 104 are supported within a housing 70 and respective cylinder heads 75, 76, 77, and 78 bolted thereto. Depending on the particular compression mechanism structure, a valve seat having an intake valve or a- discharge valve for the piston is provided in the first stage compression section 101 through the fourth stage compression section 104.
With reference to FIG. 6, sealing state of the cylinder 71 in the first stage compression section 101 will now be discussed. Two seal grooves 80 are provided on the outer peripheral surface of the cylinder 71. Seal rings (O rings) 81 are respectively disposed in the two seal grooves 80. The sealing between the members surrounding the cylinder 71 (in this case, the housing 70 and the cylinder head 75) and the cylinder 71 is provided by the seal rings (O rings) 81 being compressed between the cylinder 71 and the housing 70 and between the cylinder 71 and the cylinder head 75. Reference numeral 82 denotes a piston ring provided in the piston 51.
In order to reinforce the sealing in the above-described prior art, strong compression of the seal rings (O rings) 81 is required. However, the assembly of the seal rings (O rings) 81 with the cylinder 71, the housing 70, and the cylinder head 75 becomes more difficult. In order to achieve a suitable sealing state, the depth and width of each of the seal grooves 80 with respect to each of the seal rings (O rings) 81 become more critical. Therefore, high accuracy is required for the processing of the seal grooves 80 to be provided along the periphery of the cylinder in connection with the dimension of the seal rings (O rings) 81. Thus, a seal mechanism which realizes a simplified processing of the cylinder and an easy assembly process is required.
In view of the problems as described above, an object of the present invention is to provide a multistage high pressure compressor which has a device capable of supporting a rotor with respect to a rotating shaft of an electric motor and suppressing a torque fluctuation of the electric motor. Moreover, another object of the present invention is to provide a multistage high-pressure compressor in which a stable operation of the electric motor can be obtained.
In order to achieve the above-described objects, the present invention employs technical means such that a rotor of an electric motor is supported with respect to a rotating shaft by a fly wheel attached to a lower end of the rotating shaft of the electric motor.
The present invention also employs technical means such that the fly wheel is connected to the lower end of the rotating shaft of the electric motor by a bolt, and an extension of a detent key between the rotating shaft of the electric motor and the rotor of the electric motor is inserted into the fly wheel.
The present invention also employs technical means such that the lower end of the rotating shaft of the electric motor and the fly wheel to be attached thereto are thread-coupled by screws mating with each other, which are formed in the lower end of the rotating shaft of the electric motor and the fly wheel.
The present invention also employs technical means such that the lower end of the rotating shaft of the electric motor and the fly wheel to be attached thereto are joined by shrink-fitting therebetween.
According to the present invention, the circular plate used to support the rotor in the prior art can be eliminated, and the fly wheel is provided instead, which plays the role of supporting the rotor and can also ensure a smooth rotation of the rotor. Therefore, the vibration of the multistage compression device can be reduced. Moreover, the temperature of the coil of the electric motor used in the multistage compression device can be decreased, thereby improving the reliability of the multistage compression device.
In addition to the above-described effects, since the extension of the detent key is inserted into the fly wheel, there is provided a sufficient effect of preventing the fly wheel from rotating with respect to the rotating shaft without having to screwing the fly wheel with a bulky bolt. Both the rotor and the fly wheel can be stopped from rotating by using a common key, thereby reducing the number of components and the number of assembly steps.
Furthermore, the fly wheel is attached to the rotating shaft by joining screws formed in the fly wheel and the rotating shaft. Therefore, in addition to the above-described effects, the bolt for fixing the fly wheel with respect to the rotating shaft is no longer necessary, thereby reducing the number of components and facilitating the fixing of the fly wheel.
Also, the fly wheel is attached to the rotating shaft by shrink-fitting. Therefore, in addition to the effects of the first invention, the bolt for fixing the fly wheel with respect to the rotating shaft is no longer necessary, thereby reducing the number of components and achieving the firm fixing of the fly wheel.
Moreover, in view of the problems as described above, an object of the present invention is to provide a multistage high pressure compressor including a seal mechanism which can provide a sufficient sealing effect and can achieve a simplified processing of the cylinder and an easy assembly process. Therefore, as the particular means for solving the above-described problems, the present invention employs technical means such that seal spaces in which seal rings are respectively compressed between the cylinder and members surrounding thereof are provided at the outer peripheries at both ends of the cylinder in a multistage high pressure compressor having a compression mechanism section which generates a high pressure working fluid by reciprocating a piston utilizing the rotation of an electric motor with respect to the cylinder, and compressing the intake working fluid through a plurality of compression stages utilizing the reciprocation of the piston.
According to the present invention, since the seal spaces in which the seal rings are respectively compressed between the cylinder and the members surrounding thereof are provided at the outer peripheries at both ends of the cylinder, the processing of the cylinder is facilitated as compared to that of a cylinder such that a seal groove is formed along the mid portion of the outer periphery thereof. Also, in the assembly, it is no longer necessary to perform the cumbersome process as in the prior art of moving the seal ring from one end of the cylinder to the seal groove provided in the outer peripheral surface of the cylinder and fitting the seal ring along the seal groove.